This paper describes a series of 2-D flow visualization experiments which simulated the water coning problems encountered by a single oil production well during bottom water drive and the mitigation of these problems using Borden C302 (a phenol-formaldehyde copolymer formulation) to form gel block. The objectives of the experimental study were:
to understand the mechanisms of anti-water coning process using phenol-formaldehyde gels;
examine the feasibility of using phenol-formaldehyde gels for anti-water coning process; and
to generate suitable data for validation of numerical models developed for gel processes.
This study demonstrated that:
Phenol-formaldehyde gel could be successfully emplaced in the top part of the water cone that allowed diversion of injected water around the gel block and resulted in better sweep of the oil zone.
Anti-water coning process using gels is technically feasible as incremental oil production was observed after all gel treatments in the experiments conducted in this study. However, the effect of the gel treatment appeared to be short lived.
Suitable experiments data developed from the well defined experiment conducted in this study, could be used to validate numerical models developed for gel processes. These numerical models are useful tools for conducting detailed optimization study and economical evaluation of the gel processes before field application.
Gels are frequently used in field applications to treat oil production wells with high water-cut in an effort to reduce water or increase oil production. A survey of these field applications of gel treatments has been given by Sight and Liang1. Their review demonstrated that gel treatments have been applied over a remarkably wide range of conditions. Unfortunately, the success rates for these projects have been very sporadic. To improve the success rate for gel applications, the nature of the water production problem. The proper and realistic location for gel emplacement and the mechanisms for water diversion after get emplacement must be adequately understood. In general, gels used in the field can be classified into two type:
grain-coating and
pore-filling.
The grain-coatinggel (ex. Cr3+-polyacrylamide or Cr3+-xanthan gel) absorbs on the surface of the sand grain, forming a dense layer on pore walls. This hydrophilic polymer layer greatly reduces the mobility of the wetting fluid (i.e. water), which tends to flow close to the pore wall but has substantially less effect on the mobility of the non wetting fluid (i.e. oil or gas), which flows through the center of the pores. On the other hand, the pore-filling (ex. Phenolfomaldehyde gel) acts as a pore-blocker which greatly reduces the mobilities of both the wetting and the non wetting fluids. In field applications, grain-coating type of gels are widely used in non-thermal processes and are believed not suitable for thermal processes due to the breakdown of these gels at high temperatures. The pore-filling type of gels are more suitable for thermal processes as phenol-formaldehyde gel was demonstrated by Law et al.2 to resist temperature as high as 200 °C. In this study, the main interest is ultimately in studying antiwater cotting process using pore-filling type of gels in thermal applications in heavy oil reservoirs.
